[Infowarrior] - Quantum cryptography broken

[Richard Forno]

Quantum cryptography broken

KurzweilAI.net, April 20, 2008

Two Swedish scientsts, Jorgen Cederlof, now of Google, and Jan-Ake Larsson
of Linköping University, have found a security weakness in the quantum
cryptography authentication process--and have devised a proposed solution.

In a paper published in IEEE Trans. Inf Theory, 54: 1735-1741 (2008), they
point out that an eavesdropper could gain partial knowledge on the key in
quantum cryptography that may have an effect on the security of the
authentication in the later round.

By accessing the quantum channel used in quantum cryptography, the attacker
can change the message to be authenticated (since the message is influenced
by attacker-initiated events on the quantum channel). This, combined with
partial knowledge of the key (transmitted on the quantum channel), creates a
potential security gap, they suggest.

Their proposed solution: simply transmit an extra exchange of a small amount
of random bits on the quantum classical (Internet) channel.


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